1. Field of the Invention
This invention relates to a roll-formed, submersible electric motor for a well pump wherein motor laminations are compressed between an end ring and a coupling base while an outer metallic shell is formed to grippingly engage the ring and base, thereby maintaining the components in assembled relationship. The coupling base has fluid conduits for circulation of coolant to an armature bearing, and the base also has structure for contacting one end of a stack of pump stages and maintaining the latter in aligned relationship to the pump drive shaft.
2. Description of the Prior Art
Construction of a reliable, efficient submersible electric pump motor has long been a challenge reserved for the most experienced engineers. The motor must be designed to easily fit within the confines of four inch well pipe, yet must develop the required horsepower with high efficiency, low power consumption and long term dependability. The stator must be completely encapsulated to preclude infiltration of water under high pressures encountered in deep wells. Moreover, the various components are desirably resistant to corrosion, impact, and infiltration of water-carried abrasives, the latter of which could lead to bearing failure in a relatively short period of time.
In the past, submersible electric motor stators were commonly assembled by a procedure wherein a series of flat, ring-like laminations is securely interconnected by cleats or straps. The laminations and a plurality of stator windings are inserted between a cylindrical stator liner and an outer motor shell. A top and bottom end ring are resistance welded to the liner and shell, and epoxy is injected in an attempt to fill voids around the laminations and windings.
The upper end of a typical prior art motor has a shouldered cast iron bearing housing received in the bore of the upper end ring, and a pump-motor coupling base is bolted to the upper ring and complementally engages the bearing housing for retaining the latter in general alignment with the motor shell. Also, the base is connected to an end member of a separable pump assembly comprising a plurality of pump stages disposed in stacked relationship between the end member and an upper discharge head.
Unfortunately, such prior art motor assemblies inherently present difficulty in alignment of the armature bearings. Initially, the upper and lower end rings need be maintained in parallel and coaxial alignment during welding of the outer shell and inner stator liner to the rings. Subsequently, the bore of both of the rings must be machined for axial alignment and the end faces of the rings must be machined for parallelism. Furthermore, both of the bearing housings must be machined at their outer, ring engaging peripheries as well as their inner bores. Obviously, this multiplicity of the various machining operations results in an additive buildup of tolerance limits such that each of the machining operations must be precisely kept within a relatively small, specified error list.
Moreover, machining of such motor assemblies is rendered difficult by the size of the outer motor shell in relation to the laminations. Such laminations are of a diameter somewhat smaller than the inner diameter of the shell in order to easily insert the laminations within the shell during assembly. However, during injection of the encapsulating epoxy in the voids surrounding the windings, some of the epoxy might fill a portion of the gap between the outer edge of the laminations and the shell, while in other areas of the motor, little or no epoxy might flow into the gap between the laminations and the shell. As a result, the exterior surface of the motor shell cannot be satisfactorily gripped during machining of the bore and face of the end rings since the partially filled gaps between the laminations and the shell precluded assurance of perfect circularity of the shell and subsequent alignment of the clamping apparatus with the desired bore location of the end rings. Instead, past practice mandated the use of relatively complex, interior clamping mechanisms which expanded to grip a recess within the motor end rings during boring and facing of the latter.
The gap between the edge of the laminations and the shell of prior motors, however small, also required the use of a separate connection for insuring ground continuity between the laminations and the outer shell. Needless to say, there is a long felt need in the art for a pioneering advance in the science of motor construction so that the numerous disadvantages as outlined hereinabove can be avoided.